WASHINGTON (AP) — The U.S. Navy and Air Force have approved a limited return to flight for their new-generation F-35 fighter jet, keeping alive the possibility that it could make an appearance at the Farnborough International Airshow in England this week.

The Pentagon announced on Tuesday that Navy and Air Force officials approved the flight resumption on Monday but imposed restrictions that will remain in effect until the cause of a June 23 engine fire is identified and corrected.

The entire fleet of nearly 100 planes was grounded after the fire at Eglin Air Force Base in Florida. Initially the military declared a temporary suspension of F-35 flight operations while a safety investigation was conducted. But military leaders later halted all flights and ordered inspections of the F-35 engines to determine whether there was a systemic problem or the issue was limited to the one damaged aircraft.

The Pentagon’s announcement Tuesday did not give any investigation details. It said additional information would be provided later.

Farnborough would be the plane’s first overseas air show.

The Pentagon’s press secretary, Navy Rear Adm. John Kirby, said Tuesday that officials “remain hopeful” that the F-35 can make an appearance at Farnborough.

He said the limited return to flight was encouraging but no final decision has been made on the air show.

The F-35 is the Pentagon’s most expensive aircraft program, costing an estimated $400 billion.

Three variants of the aircraft are being developed and built, one each for the Air Force, Navy and Marine Corps.

The Marines expect to field their version next summer, the Air Force will follow in 2016, and the Navy a year after that. International buyers include Britain, South Korea, Israel, Italy, Australia, Canada, Turkey and Japan.

Members of Congress, however, have complained that the program has been troubled with testing problems, delays and cost overruns. The jet is intended to replace Cold War-era aircraft such as the Air Force F-16 fighter, the Navy’s F/A-18 Hornet and the Marines’ EA-6B Prowler and AV-8B Harrier.

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